title: Prospective study of natural history of deep vein thrombosis: early predictors of poor late outcomes.
abstract: BACKGROUND
  A proportion of patients with deep vein thrombosis (DVT) will develop postthrombotic syndrome (PTS). Currently, the only clearly identified risk factors for developing PTS are recurrent ipsilateral DVT and extensive proximal disease. The aim of the study was to assess the natural history of DVT and identify early predictors of poor clinical outcome at 5 years.
  
  
  METHODS
  Patients with suspected acute DVT in the lower limb were assessed prospectively. All patients with a confirmed DVT were asked to participate in this study. Within 7-10 days after diagnosis of DVT, patients underwent a further review, involving clinical, ultrasound, and air plethysmography assessment of both lower limbs. Patients were reassessed at regular intervals for 5 years.
  
  
  RESULTS
  One hundred twenty-two limbs in 114 patients were included in this study. Thrombus regression occurred in two phases, with a rapid regression between 10 days and 3 months, and a more gradual regression thereafter. Reflux developed as thrombus regression occurred. Segmental reflux progressed to axial deep reflux and continued to deteriorate in a significant proportion of patients with iliofemoral-popliteal-calf DVT throughout the 5-year study period. Similarly, venous filling index became progressively more abnormal, in this group, over the course of the study. Four risk factors for PTS were identified as best predictors: extensive clot load on presentation; <50% clot regression at 6 months; venous filling index >2.5 mL/sec; and abnormal outflow rate (<0.6). Patients with three or more of these risk factors had a significant risk of developing PTS with sensitivity 100%, specificity 83%, and positive predictive value 67%. Patients scoring 2 or less did not have PTS at 5 years with a negative predictive value of 100%.
  
  
  CONCLUSIONS
  This is the first study to show that venous assessment at 6 months post-DVT can predict PTS at 5 years. Those who will not develop PTS can be reassured of this at 6 months.
authors.affiliation: Department of Surgery, Dunedin School of Medicine, University of Otago, Dunedin, New Zealand. andre.vanrij@otago.ac.nz
authors.forename: André M
authors.initials: AM
authors.lastname: van Rij
authors.forename: Gerry
authors.initials: G
authors.lastname: Hill
authors.forename: Jo
authors.initials: J
authors.lastname: Krysa
authors.forename: Samantha
authors.initials: S
authors.lastname: Dutton
authors.forename: Riordon
authors.initials: R
authors.lastname: Dickson
authors.forename: Ross
authors.initials: R
authors.lastname: Christie
authors.forename: Judi
authors.initials: J
authors.lastname: Smillie
authors.forename: Ping
authors.initials: P
authors.lastname: Jiang
authors.forename: Clive
authors.initials: C
authors.lastname: Solomon
mesh_terms: D000208:Acute Disease; D000328:Adult; D000368:Aged; D016009:Chi-Square Distribution; D005260:Female; D006439:Hemodynamics; D006801:Humans; D016015:Logistic Models; D035002:Lower Extremity / Q000098:blood supply*; D008297:Male; D008875:Middle Aged; D015999:Multivariate Analysis; D010991:Plethysmography; D054070:Postthrombotic Syndrome / Q000175:diagnosis / Q000209:etiology* / Q000503:physiopathology / Q000517:prevention & control; D011237:Predictive Value of Tests; D011446:Prospective Studies; D018570:Risk Assessment; D012307:Risk Factors; D053828:Stockings, Compression; D013997:Time Factors; D016896:Treatment Outcome; D018616:Ultrasonography, Doppler, Duplex; D020246:Venous Thrombosis / Q000150:complications* / Q000175:diagnosis / Q000503:physiopathology / Q000628:therapy